This invention relates to a nuclear power plant containment system and in particular to a method and apparatus for the removal of hydrogen from the containment atmosphere using a gas permeable membrane separator.
During the operation of a water cooled nuclear reactor, hydrogen and oxygen are formed by the radiolytic decomposition of water. Systems designed to combine the hydrogen and oxygen gases are called recombiners. Gas recombiners can be categorized as the catalytic, convection, condenser, diffusion, thermal or forced flow types. These recombiners recombine hydrogen with oxygen from the containment atmosphere and return the recombined products to the containment atmosphere. These types of gas recombiners are generally small in capacity while large in physical size. The forced flow type is not limited in capacity but requires the use of gas pumping systems as well as a carrier gas.
The capacity of present hydrogen recombiners is sufficient to handle the hydrogen generated in normal operation of a nuclear reactor. However, large quantities of hydrogen may be generated by dissociation of water during an accident condition that will require releasing the hydrogen from the reactor vessel to the reactor containment building. Present hydrogen recombiners are designed to process about 39.2 cubic meters per minute (50 cubic feet per minute) of containment atmosphere. Present recombiners do not have the capacity to handle the quantity of hydrogen generated during an accident condition and would require an increase in capacity by a factor of approximately 100 to 400. In view of the power requirements and physical size of an increased capacity recombiner, an increased capacity recombiner or prior art design does not appear to be practical.
Therefore, a need exists for a method and apparatus for removing hydrogen gas from a combination of gases during the large scale hydrogen releases of a nuclear power plant accident condition. Such a method and apparatus would separate the hydrogen from the containment atmosphere for disposal independent of the containment atmosphere and use equipment of reasonable size while minimizing system power requirements.